Abstract: A developing unit has a voltage-applicator (80) to apply a developing bias voltage to a developing roller (72). The voltage-applicator (80) applies the developing bias voltage for a first duration to apply an AC voltage having a rectangular waveform, and a second duration to stop applying the AC voltage. The AC voltage has a duty ratio of 50% or more in a direction for causing toner to develop an electrostatic latent image. The number of cycles of the AC voltage in the first duration is two or more, and the AC voltage has a voltage in a direction for pulling the toner back to the developing roller, just before transition to the second duration. The developing unit suppresses occurrence of image unevenness due to a fluctuation in developing gap. Thus, an image forming apparatus equipped with the developing unit forms a high-quality image while suppressing image unevenness.

Abstract: An image forming apparatus having a touchdown-development type developing apparatus, in which a toner collecting roller that collects scattered toner suspended in the vicinity of a toner holding body and a two-component developer holding body is arranged on the downstream side in a rotational direction of the two-component developer holding body from a closest position of the two-component developer holding body and the toner holding body, and between the two-component developer holding body and the housing wall, and further, bias means that applies a bias voltage for collecting the scattered toner to the toner collecting roller, and image density sensing means for sensing a density of a toner image developed on the electrostatic latent image holding body surface or a toner image on a transfer body onto which the toner image developed on the electrostatic latent image holding body surface is transferred to control the bias voltage are provided.

Abstract: An image forming apparatus includes a latent image carrying member, a two-component developer carrying member holding on an outer surface a developer containing carrier beads and toner particles, the two-component developer carrying member having a first magnetic element mounted therein, a toner carrying member carrying a thin toner layer on an outer surface, a toner collecting roller for collecting the toner particles scattered and suspended in the vicinity of the two-component developer carrying member and the toner carrying member, the toner collecting roller having a second magnetic element mounted therein, and a housing accommodating the two-component developer carrying member, the toner carrying member and the toner collecting roller. The toner collecting roller is located face to face with the two-component developer carrying member with the first and second magnetic elements disposed to face each other with oppositely directed polarities.

Abstract: In an image forming apparatus, a control section 41 adjusts the surface potential of a photoconductor or the developing potential of a developer carrying member based on the detection result of a surface potential sensor 44, and performs first correction whereby, relative to the reference value of the applied bias of a charger 2 or the developing bias of the developer carrying member in a developing unit 4 as observed during potential adjustment, the applied bias or the developing bias is varied so as to keep constant the potential difference between the surface potential of the photoconductor and the developing potential of the developer carrying member during image formation. The control section also performs second correction whereby the applied bias or the developing bias is restored to the reference value over a predetermined period after the completion of continuous image formation.

Abstract: The electrophotographic image formation apparatus of the present invention adopts a developer roller, which is made of aluminum and has an aluminum oxide film of at least 5 ?m in thickness formed on surface thereof. In the image formation apparatus, a gap between the developer roller and a photoreceptor drum 3 is set in a range of 150 to 300 ?m. The image formation method of the present invention regulates a frequency of AC voltage in a non-development state to be higher than that in a development state, when an AC voltage is applied onto the developer roller to cause flight of toner from the developer roller to the photoreceptor, and selectively makes charged toner fly onto the electrostatic latent image for development. The present invention provides the effective development technique to prevent leakage of the applied voltage between the developer roller and the photoreceptor drum.

Abstract: Disclosed are image forming apparatus [1] which comprises removing a toner remained on the surface of the rotatable image carrier by cleaning means after going through developing means and transferring means; said cleaning means has an elastic blade and is contacted with the surface of the image carrier at a contact pressure within 8 to 20 g/cm, and a press-contact angle of the elastic blade of 12 to 30°; and said image carrier is an organic photosensitive material having a photosensitive layer made of a binder resin containing an electric charge generating material and an electric charge transferring material; and image forming apparatus [2], comprising a single-layer type photosensitive layer made of a binder resin containing an electric charge generating material, an electron transferring material and a hole transferring material, and the solid content of the binder resin is within 50 to 70 wt % of the whole solid content in the photosensitive layer and, a pair of paper transporting rollers are arranged on

Abstract: The electrophotographic image formation apparatus of the present invention adopts a developer roller, which is made of aluminum and has an aluminum oxide film of at least 5 &mgr;m in thickness formed on surface thereof. In the image formation apparatus, a gap between the developer roller and a photoreceptor drum 3 is set in a range of 150 to 300 &mgr;m. The image formation method of the present invention regulates a frequency of AC voltage in a non-development state to be higher than that in a development state, when an AC voltage is applied onto the developer roller to cause flight of toner from the developer roller to the photoreceptor, and selectively makes charged toner fly onto the electrostatic latent image for development. The present invention provides the effective development technique to prevent leakage of the applied voltage between the developer roller and the photoreceptor drum.

Abstract: Disclosed are image forming apparatus [1] which comprises removing a toner remained on the surface of the rotatable image carrier by cleaning means after going through developing means and transferring means; said cleaning means has an elastic blade and is contacted with the surface of the image carrier at a contact pressure within 8 to 20 g/cm, and a press-contact angle of the elastic blade of 12 to 30°; and said image carrier is an organic photosensitive material having a photosensitive layer made of a binder resin containing an electric charge generating material and an electric charge transferring material; and image forming apparatus [2], comprising a single-layer type photosensitive layer made of a binder resin containing an electric charge generating material, an electron transferring material and a hole transferring material, and the solid content of the binder resin is within 50 to 70 wt % of the whole solid content in the photosensitive layer and, a pair of paper transporting

Abstract: In a transfer method of this invention, a paper powder-removing device having a pair of an insulating roller and an electrically conducting roller is provided on a transfer paper conveyer passage, and a transfer paper is passed through between a pair of the above rollers prior to being fed to a transfer zone (between a transfer roller and a photosensitive material drum). The transfer paper is passed through the pair of rollers in a state where the electrically conducting roller is maintained at a potential of a polarity same as, or opposite to, that of the transfer roller depending upon the position of the electrically conducting roller (position on a side of the transfer surface of the transfer paper or position on a side opposite to the transfer surface) in the paper powder-removing device, in order to reliably remove the paper powder from the transfer paper and to effectively prevent the adhesion of the paper powder on the surface of the photosensitive material drum.